This invention relates to a method for elevated-temperature hard-material coating or heat treatment of the blade airfoils of blisks of aircraft gas turbines and an apparatus for the performance of this method.
High-pressure compressors of aircraft turbines can be equipped with blisks where the actual disk, the blade platforms and the blade airfoils are manufactured as one integral part. In order to improve protection against wear by particles carried by the compressed air, the blade airfoils, as is generally known, are coated, for example, by means of an elevated-temperature plasma vapor deposition process using hard materials, such as nitrides or carbides. Further, after repair of the blade airfoils, the blisks are subject to a heat-treatment process. The coating or the heat-treatment processes, respectively, are, however, disadvantageous in that, simultaneously with the blade airfoils, the blade platforms and the actual disk are heated to a temperature that exceeds the maximum operating temperature. While this high process temperature does not constitute a serious problem for the less loaded stressed blade airfoils, it can cause geometrical distortion, affect serviceability and, ultimately, lead to a reduction of service life of the other parts of the blisk.